Telecommunication systems often take advantage of secondary use of radio spectrum and communication channels to maximize the use of frequency bands with advantageous performance characteristics and manage these limited frequency bands within a geographical region. For example, in the United States, the Federal Communications Commission (FCC) may issue primary and secondary users licenses to operate in the same frequency band, with the stipulation that the secondary user cannot cause, or at least minimize, harmful interference to the primary user. One example of this is in air-to-ground (ATG) communication systems that act as secondary users together with primary Ku band satellite users. ATG communication systems typically provide a direct line of site between the aircraft stations (AS) and the ground stations (GS), for example by providing connectivity to commercial aircraft that fly at 10,000 feet or above.
The radio propagation conditions of ATG systems differ significantly from conventional cellular systems for ground coverage. One particular difference relates to the low frequency selectivity of the frequency bands air-to-ground communication systems operate due to the absence of ground-based scatterers. These conditions allow simplification of systems in the scheduling of radio resources that otherwise require additional complication in ground-based only systems. However, as air-to-ground communication systems are assigned as secondary users of the frequency spectrum, additional restrictions are added to the system, in particular related radiated power and the spatial configurations to avoid interfering with primary users.
4G cellular technologies, like Long-Term Evolution (LTE), possess efficiency advantages, able to work with wide bandwidths, and scale easily to even larger bandwidths with features such as carrier aggregation. However, the current LTE specification requires significant signaling on the control channel to manage the diverse channel conditions that the specification supports. Employing a direct use of the LTE type specification on an ATG system would require a robust control channel in all frequency carriers which cannot always be guaranteed, particularly in the case of secondary frequency use.
Techniques to reduce scheduling grants that minimize or eliminate the use of control channels, at the expense of flexibility, allow lower transmit power on the control channels reducing the interference to the primary system. One embodiment includes use of a single grant to allocate a set of resources across all carriers, or communication channels. This simplification comes at the cost of retransmission of data for all carriers in the case if interference corrupts the transmission of a subset of the carriers. Complementing the single grant embodiment with detection of the affected frequency carriers or victim carriers and remove such carriers from the carrier aggregation configuration allows more efficient use of the allocated spectrum. Therefore, scheduling of multiple carriers with a single grant complemented with a method to perform interference detection may provide significant advantages, particularly in an ATG use case.